1. Field of the Invention
The present invention relates to an edger for trimming grass and soil at an edge of a grassland such as a grassy lawn adjacent to a pavement, building or the like.
2. Description of Prior Art
In general, an edger of this kind includes a rotatable motor driven cutter blade arranged at the side of a travelling body or edger vehicle having wheels, and is controlled by an operator so that an edge of the grassland is trimmed by the edger as he manipulates rear operating handles.
In a cutter device of a conventional belt driven edger, the cutter drive belt is clutched or engaged by increasing the distance between two pulleys as the bearing housing of one pulley is moved away from the other pulley as by a swing arm. The swing arm also serves as the mechanism for adjustment of the cutter depth once the clutch has been engaged.
A first type of conventional belt driven edger provides a clutch lever at the rear operator station of the edger such that when the lever is pulled back by the operator, a linkage mechanism rotates the swing arm downward, thus engaging the drive belt. When the clutch lever is released by the operator, the swing arm is rotated upward by the force of a spring, thus disengaging the drive belt. The depth of the cut is adjusted at the side of the edger frame when the clutch is disengaged by adjusting the length of the linkage mechanism. Changing the length of the linkage mechanism will change the distance that the swing arm is rotated downward, thus changing the depth of the cut.
This first type of conventional belt driven edger disengages the clutch mechanism upon release of the clutch lever by the operator but permits the depth of cut to only be adjusted by disengaging the clutch and interrupting the edging operation.
A second type of conventional belt driven edger provides a control lever at the rear operator station of the edger that controls the rotation of the swing arm through a linkage mechanism. The swing arm is moved downward to engage the belt by shifting the control lever from its neutral position to a first position setting recess. The swing arm is further lowered and the depth of cut consequently increased by shifting the control lever into successive position setting recesses. The depth of the cutter blade is adjusted by shifting the control lever to different position setting recesses, and the belt is disengaged only when the operator returns the control lever to the neutral position.
This second type of conventional belt driven edger provides for cutter depth adjustment while the belt is engaged without interrupting the edging operation. However, it does not provide for a clutch disengagement when the operator leaves the operator station.
Further, neither type of conventional belt driven edger provide a mechanism for quickly stopping the rotation of the cutter blade when the drive belt has been disengaged.
Further, the wide range of upward and downward swinging movement of the swing arm makes it difficult to use a fixed belt cover for the whole belt driving device. A forward cover for the front driven pulley and a rear cover for the rear driving pulley must be independently arranged on conventional edger clutches, or a swingable cover must be provided, thus requiring costly manufacture and/or attachment of the belt cover.
Still another type of conventional edger drives the cutter blade by a driving shaft instead of a belt and employs a conventional centrifugal clutch. The operator engages the clutch by pulling back a clutch lever at the operator station. The clutch becomes disengaged and the cutter blade eventually stops when the operator releases the clutch lever.
The cutter blade is rotatably fixed to the edger frame and the depth of the cut is adjusted by adjusting the front wheel in an up-and-down direction. By adjusting the position of the front wheel, the height of the frame above the ground is adjusted, as well as the depth of the cutter blade which is fixed to the frame.
This conventional shaft driven edger provides for disengagement of the clutch as the operator leaves the operator station. It also provides for adjustment of the cutter depth while the clutch is engaged without interrupting the edging operation. However, as the blade encounters obstructions, the driving shaft receives the shock loads and transfers them to the engine which could potentially damage the engine.